HEI - Head End Ignition
Please review the HEI Information page to get a general overview.
For staged rockets, the second stage has to be ignited near Vacuum space. We need a system that can raise the pressure in the chamber while increasing the temperature to reach combustion conditions.
Design Changes and Verification
Forward Closure
With respect to the HEI used in the staging demonstrator, we increased the wall thickness and added a fillet between the base and the wall.
To calculate the MoS we use an ID of 1.375 in, an OD of 1.842 in, and the maximum pressure of the Sustainer with 826 psi.
\sigma_H = \frac{P*r}{t} = \frac{(826 psi)*\frac{1.375 in}{2}}{\frac{1.842in-1.375in}{2}} = 2432.01 psi
6061-T6 Aluminum has a yield stress of 40000 psi.
MoS = \frac{40000 psi}{2432.01 psi} -1 = 15.4
Thus, the margin of safety is much more than the required minimum of one, which makes us confident that the wall will not yield.
Nevertheless, we would not decrease the wall thickness since we want to avoid radial tore of the bolts.
Bolts
O - Rings
We changed to 230 and 229 O rings. Verify all O rings including 121 and 122
Igniter Grain
No Change, show open motor curve and talk about funny canted nozzles
Manufacturing
include drawings of all parts, where we get them from, and how to machine it
Integration
Custom E-Matches
Saftey